What is the rate of reaction and how is it measured?

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What affects the rate of reaction?

Reshmal Barot

                    Change in amount of substance

Rate of reaction =

   Time taken for the change to occur

What is the rate of reaction and how is it measured?

The phrase rate of reaction means how fast is the reaction. It can be measured as the rate of formation of product or the rate of disappearance of reactant.

Aim

This experiment involves investigating factors that influence the rate of reaction. I will see if a reaction becomes faster or slower by altering certain conditions. The condition that I will be altering is the concentration of one of the reactants. The reaction I will be investigating is between calcium carbonate and hydrochloric acid.

Equation

        The equation of this reaction is

Calcium carbonate + hydrochloric acid                       calcium chloride + carbon dioxide + water

CaCO3 + 2HCL         CaCl2 + CO2 + H2O

Factors that affect the rate of reaction

         For this experiment I will explore what affects the rate of reaction when limestone (calcium Carbonate) is added to hydrochloric acid. Some variables that can influence the rate of reaction are:

  • Concentration of acid (how many molars it has) – if the concentration is increased, there is likely to be more collisions between the particles therefore activating the chemical reaction between them more often, thus making the reaction occur faster.
  • Increasing the concentration, increases the probability of a collision between reactant particles because there are more of them in the same volume.

Example:

         Increasing the concentration of acid molecules increases the frequency or chance at which they hit the surface of marble chips to dissolve them (slower               faster).

        Increasing the concentration of reactant A or B will increase the chance or frequency of collision between them and increase the speed of product formation (slower             faster). 2                                                                                        2- /www.wpbschoolhouse.btinternet.co.uk

  • Increasing the temperature – when the temperature is increased it makes the particles move around quicker and more vigorously, because of this they collide more often and make the reaction happen a lot faster. Also a greater amount of energy is produced.

  • Increasing the pressure – when the pressure is increased it has the same kind of effect as increasing the concentration. It brings particle closer together and forces them to collide and produce more energy.
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  • The surface area of the particles – When the surface area of the reactant is increased more atoms are exposed and therefore available for collision. The surface area of the particles that we are using (calcium carbonate) can be increased by crushing it up.

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1www.wpbschoolhouse.btinternet.co.uk/page03/3_31rates.htm

Smaller pieces have a larger surface area so there are more collisions and therefore a faster reaction.

  • Using a catalyst- A Catalyst is a substance that alters the rate of reaction but remains chemically unchanged at the end ...

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